The invention relates to a channel spark source for generating a stable focused electron beam comprising, in a co-axial arrangement, a dielectric tube, in which a trigger plasma is generated, and, adjacent thereto, a hollow cathode, a dielectric channel spark body ending at an anode with a central passage, a dielectric tube in alignment with the channel spark body, a condenser connected as an electric energy storage device to the anode and the cathode, an electrode connected by way of a spark gap to a reference potential and an electric resistance bridging the electrode and the hollow cathode. The arrangement corresponds in principle to the arrangement as described in German publication 42 08 764.
The life of the channel spark tube described in DE 198 49 894 is only about 1 million shots. Then the beam has cut a passage into the tube housing wall. Another disadvantage resides in the generation of heat. Beginning at about 50 Hz pulse frequency, a red hot area can be observed in the channel spark tube. At 100 Hz pulse frequency, the tube is heated to a white hot state because of the energy loss.
In order to satisfy industrial standards lifespans of 109 pulses are required as they are standard with Excimer lasers. In an actual situation, the electric power output of the channel spark system is limited at 50 Hz pulse frequencies to about 150 W and the radiation power output is limited to about 60 W. In comparison with other laser or respectively particle accelerators (electron cannon) whose power output is in the 1 KW range, the present power output capability of the channel spark system is too small to serve as a source for process energy.
The reason for the chaotic movement of the beam in the channel spark system, particularly in the area of the anode-side channel spark tube and after leaving this tube is an instability which is similar to the so-called hose instability z-pinches. From the operation of channel spark apparatus, it is known that this instability occurs only after an extended period of operation (about 10000 shots), apparently after the system is warmed up and fully degasified.
It is the object of the present invention to improve existing channel spark gaps or sources in such a way that very high shot numbers of constant beam quality can be achieved and such an improved channel spark source are usable in an industrial plant.